net: ethtool: correct MAX attribute value for stats

When compiling YNL generated code compiler complains about
array-initializer-out-of-bounds. Turns out the MAX value
for STATS_GRP uses the value for STATS.

This may lead to random corruptions in user space (kernel
itself doesn't use this value as it never parses stats).

Fixes: f09ea6fb

 ("ethtool: add a new command for reading standard stats")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>